Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
It is known to use an FCL in an electrical distribution system (EDS) to protect infrastructure—and in particular to protect a transformer in an EDS—during fault conditions. These FCLs are by necessity large devices that carry the load current at the load voltage and are required to meet all the necessary standards for use at those levels of current and voltage.
Those FCLs that have been developed for commercial use typically include at least one coil of high temperature superconductor (HTS) that is disposed about a core. For laboratory testing purposes there has also been use made of small-scale test devices constructed from more traditional conductors. The latter are, however, not rated for continuous use and are not constructed for practical use in an EDS.
A HTS FCL is typically categorised as an inductive FCL—where the load current flows through a metal coil—or a resistive FCL—where the current flows thought the superconductor coil. For an inductive FCL use is made of a HTS DC bias coil for biasing the core into saturation at least in the vicinity of the metal coil. This bias is such that a flow of current through the metal coil above a given threshold will result in the core being progressed out of saturation which, in turn, will change the inductance of the metal coil and have a limiting affect upon the load current.
The use of a HTS coil is problematic in some applications due to it being more maintenance intensive, more expensive to purchase, more difficult to manufacture, and it requires more overall footprint due to the need for associated cooling equipment.